Lubricating oil compositions, as used in the internal combustion engines and transmissions of automobiles or trucks, are subjected to a demanding environment. This environment results in the lubricating oil composition suffering oxidation that is catalyzed by the presence of impurities in the lubricating oil composition, such as iron compounds. Additionally, oxidation of the lubricating oil composition is promoted by the elevated temperatures of the lubricating oil composition during use.
The oxidation of the lubricating oil composition during use is usually controlled to some extent by the use of additives, such as antioxidants or acid neutralizers, which may extend the useful life of the lubricating oil composition, particularly by reducing or preventing unacceptable viscosity increases.
Acid neutralizers generally used in lubricant compositions may be selected from metal alkyl phenates and metal alkylaryl sulfonates. The metal of the metal of the phenates and sulfonates may be selected from alkali and alkaline earth metals such as calcium, magnesium, sodium, or barium.
In recent years, phosphorus compounds and sulfur (from sulfonates, sulfur-containing phenates, and metal-containing dithiophosphates) derived from engine lubricants have been shown to contribute in part to particulate emissions. Also, sulfur and phosphorus tend to poison the catalysts used in catalytic converters, resulting in a reduction in performance of the catalysts.
Accordingly, there exists a need for improved lubricant compositions that have reduced levels of sulfur and phosphorus. By reduced levels is meant less than 1.0 wt. % phosphorus and less than 0.5 wt. % sulfur based on the total weight of the lubricant composition.
In view of the foregoing, an embodiment of the disclosure provides sulfur-free metal or ammonium salt compound, a method of making the compound, and a lubricant additive concentrate, and lubricant composition containing the compound. The compound is made by reacting a phenolic compound that has been reacted with an aldehyde and an amine, with a compound selected from the group consisting of an acylating agent or an electrophilic compound. The reaction product is then neutralized or overbased with a metal or ammonium compound.
In another embodiment, the disclosure provides a method for making a sulfur-free, metal or ammonium salt compound for use as a lubricant additive component. The method includes reacting (a) a phenolic compound with (b) an aldehyde, and (c) an amine to provide an intermediate product. The intermediate product is reacted with (d) a compound selected from the group consisting of an acylating agent or an electrophilic compound to provide a reaction product. The reaction product is then neutralized or overbased to provide the lubricant additive component.